The present invention relates to an answer supervision detection unit for pay telephone systems which detects answer supervision information signals, converts those signals into coded signals and then places the signals on communication lines that run to customer owned pay telephones.
It is known in the industry that there are three general types of telephone communications lines. The first, loop start or ground start lines utilize two wires that couple the telephone to the central office. Customarily, the central office is owned by a regional Bell operating company. The second type of line is an E & M line. The E & M lines can be two or four wire communication lines. The third type of line is a T1 or "D" type communications line.
Due to the current regulatory and tariff regulations regarding pay telephones, all customer owned pay telephones must be connected by loop or ground start lines. Pay telephones owned by the regional Bell operating companies are provided coin collect and refund signals by the central office by changing the polarity of a voltage applied across tip and ground leads to the telephone thereby signaling that pay telephone that the outgoing call has been answered, that the outgoing call is seeking a response from a phone that is busy, or other types of answer supervision. However when a customer, other than a regional Bell operating company, owns the pay telephone, no answer supervision is passed from the central office of the operating company to the pay telephone. These customer owned telephone systems are sometimes called COCOTS which refers Customer Owned Coin Operated Telephone Systems or COPS which refers to Customer Owned Pay Stations.
For example, if a restaurant wished to own a pay telephone, the current regulations permit such ownership. However, when that customer owned pay telephone is connected to the central office, answer supervision to the phone by the central office is no longer provided in accordance with established tariffs. The inability to obtain answer supervision at the customer owned pay telephone can cause significant difficulties regarding obtaining payment for the use of the telephone from the user to the independently owned coin operated telephone.
For example currently, the user removes the hand set of the telephone off the hook and immediately hears dial tone. This is a characteristic of a loop start dial tone first line. The user then inserts a prescribed amount of money, such as a quarter. The user then dials the telephone number. In some COCOT pay phones, the telephone monitors the time from the completion of the dialing in order to determine whether to accept the quarter or to return the quarter to the user. Typically, most customer owned pay phones wait a time span approximately seven or 10 rings before accepting the quarter. If the user allows the phone to ring more than the predetermined time span, he will not be able to obtain the return of the quarter notwithstanding the fact his phone call was never answered. The same thing occurs with regard to a busy signal sent from the called end. If the user remains on the communications line long enough listening to the busy signal, the customer owned pay phone will accept his quarter and not return it since the phone simply times the length of the call to determine whether to accept or return the quarter.
Generally, this is not the case with pay phones owned by the Bell operating companies since those pay phones do coin collect or refund signals by way of the central office. Answer supervision signals are information signals sent over the public switched network that informs the central office that the call has been answered by the hand set being lifted off of the called telephone set. The central office then signals the Bell operating company pay telephone to collect or refund the coins.
This problem of determining when to accept payment is amplified when long distance calls are involved and the call is to be charged to the user's credit card or a significant amount of money is to be deposited into the phone to pay for a long distance call. Pay telephones are now in use that automatically charge the user's credit card after the user has electronically or manually input his credit number into the pay phone.
Sometimes COCOTS utilize a tandem telephone switch to achieve least cost routing of long distance telephone calls from the pay telephones owned by the COCOT. These tandem telephone switches are not usually equipped to pass answer supervision information signals coming from the called party back to the COCOT pay phones. In most cases, the calls pass through the tandem switch through the central office and then to the COCOT pay phone. Even if the tandem switch can pass any type of answer supervision, the central office blocks those answer supervision signals. In general, answer supervision on loop start telephone lines over long distances is very unreliable. On ground start lines, answer supervision is very limited. On the other hand, answer supervision on E & M lines and T1 type telephone lines is very good. Public switched networks carry long distance communications and typically use E & M lines or T1 lines. T1 telephone lines are simply digital multiplexed communications over a four wire E & M lines or like facilities. The difference between two wire E & M lines and four wire E & M lines is that four wire E & M lines operate in full duplex mode in that two wires exist for all outgoing information and two wires exist for all incoming information in addition to the E & M control lines.